Method for making acetone soluble cellulose acetate with aldehyde



Patented Oct. 10, 1933 PATENT oFFi-c METHOD FOR MAKING ACETONE SOLUBLE CELLULOSE ACETATE WITH ALDEHYDE Thomas F. Murray, Zr. and Harry Le B. Gray, Rochester, N. Y., assigncrs to Eastman Kodak Company, Rochester, "12"., a corporation of New York No Drawing. Application November 5, 1930 Serial No. 493,687

15 Claims.

This invention relates to a process for producing acetone-soluble cellulose acetate, and more particularly to a process in which acetonesoluble cellulose acetate is produced in a single acetylation step, with the aid of an aldehyde.

In the usual procedure for the production of cellulose acetate for use in the arts cellulose is aeetylated to a triacetate and subsequently partially deacetylated or hydrolyzed until a product is obtained which is soluble in acetone. Since the acetone soluble variety of cellulose acetate was first prepared, attempts have been made to find a method by which it may be made acetone soluble without subsequent hydrolysis. Such a procedure would have an enormous technical value. Because of its saving of time, space, apparatus, chemicals and labor, it would have an econoa ical advantage yet to be estimated.

The present process proposes the use of a substantial amount of an aldehyde, as an agent of addition in the acetylation of the cellulose. It has been previously known to carry out this acetylation in the presence of small amounts of formaldehyde, but the proportion used was not suflicient to produce acetone-soluble cellulose acetate, the formaldehyde being added merely for a stabilizing eiiect. In addition there are the well known diiiiculties of working with formaldehyde in any quantity. Also, previously it has not been known that the aldehydes have the function of controlling the acetylation reaction in the manner described, that is, producing acetone-soluble cellulose acetate.

We have found that the addition of acetaldehyde or other appropriate aldehyde to acetic anhydride in the acetylation of cellulose causes the formation of a cellulose derivative which is directly soluble in acetone. The procedure introduces no technical difliculties. Acetaldehyde is cheap and easily available in commercial quantities. Any unused aldehyde can be recovered or easily oxidized to acetic acid.

Specifically, the process is carried out in the following steps:

1. To about grams of air-dried cotton linters is added a mixture of about 333 cubic centimeters of glacial acetic acid and approximately two cubic centimeters of a catalyst (preferably 95% sulphuric acid and 95% phosphoric acid in the ratio of l to 3) and the mixture is allowed to stand at room temperature (23 to 25 degrees C) for about 19 hours or longer. If it is desired to eliminate this step 1, the 19 hours standing is eliminated so that all the materials are mixed together and the acetylation is then carried out, although without pre-treatment acetylation does not prov ceed as readily as with it.

2. The pie-treated cellulose of step 1 may next be treated with a mixture of about 140 cubic centimeters of 85% acetic anhydride and 17 to 18' cubic centimeters ofacetaldehyde, the whole being intimately mixed in a vessel in a water bath at a temperature of about 18 C. Stirring is continued and the bath is heated slowly and slightly for from 1 to 4 hours, after which the rate of heating is increased until a maximum of about 40 C is obtained. Stirring is continued at this temperature for a total acetylation of about 22 hours. To the dope thus obtained may be added 169 to 150 cubic centimeters of acetone to give greater fluidity to the dope, which may then be which has previously been necessary. We have also discovered the broad principle that an aldehyde may be employed to obtain acetone-soluble cellulose acetate in the acetylation step.

As low as 25 cubic centimeters of acet-aldehyde per 100 grams of linters may be employed to obtain a product which is soluble in acetone. While we have found that 35 cubic centimeters per 100 grams of linters is to be preferred, we have also found that to a cubic centimeters per 100 grams of linters is suitable in this process.

It is to be understood that the above specific example is not to limit the process as to the time, temperature and materials used, etc. Thus the time and temperature of pre-treatment may be varied as is well known, a different catalyst may be used in the acetylation process, such for instance as sulphuric acid, and the time and term perature of esterification may be changed somewhat, although it is obvious that after acetonesolubility has been obtained there is no need for further acetylation. Precipitation of the cellulose ester from the dope in which it is prepared may be accomplished in other precipitants, if desired, such as a weak acetic acid solution.

In addition to acetaldehyde, other aldehydes used instead of cotton linters and other acetylation catalysts may be used instead of the phosphoric-sulphuric mixture, as known in the art.

What we claim as our invention and desire to be secured by Letters Patent of the United States is:

1. The process of producing an acetone-soluble cellulose acetate which comprises pre-treating cellulose in concentrated organic acid in the presence of an acetylation catalyst, and acetylating the cellulosic material by adding acetic anhydride and at least 25 c.c. of an aldehyde per hundred grams of cellulose employed.

2. The process of producing an acetone-soluble cellulose acetate which comprises pre-treating cellulose in concentrated organic acid in the presence of an acetylation catalyst, and acetylating the cellulosic material by adding aceticanhydride and at least 25 c.c. of an aldehyde-containing a plurality of carbon atoms per hundred grams of cellulose employed.

3. The process of producing an acetone-soluble cellulose acetate which comprises pre-treating cellulose in concentrated acetic acid and an acetylation catalyst, and acetylating the cellulosic material by adding acetic anhydride and at least 25 c.c. of an aldehyde per hundred grams of cellulose employed.

4. The process of producing an acetone-soluble cellulose acetate .which comprises acetylating cellulose in the presence of 25-100 c.c. of an aldehyde per 100 grams of cellulosic material present. v

,5. The process of producing an acetone-soluble cellulose acetate which comprises acetylating cellulose in the presence of c.c. of an aldehyde containing a plurality of carbon atoms per 100 grams of cellulosic material present.

6. The process of producing an acetone-soluble cellulose acetate which comprises acetylating cellulose in the presence of 35 c.c. of acetaldehyde, per 100 grams of cellulosic material present.

'7. The process of producing an acetone-soluble cellulose acetate which comprises acetylating cellulose in the presence of 25-100 c.c. of acetyaldehyde per 100 grams of cellulosic material present.

8.The process of producing an acetone-soluble cellulose acetate which comprises acetylating celluose in the presence of 25-100 c.c. of an aldehyde, containing a plurality of carbon atoms, per 100 grams of cellulosic material present.

9. A process for producing cellulose acetate which comprises acetylating cellulose in acetic acid and acetic anhydride in the presence of a catalyst and at'least 25 c.c. of acetaldehyde per hundred grams of cellulose employed.

10. A process for producing cellulose acetate which comprises acetylating cellulose in acetic acid and acetic anhydride in the presence of a catalyst and paraldehyde.

ll. A process for producing cellulose acetate which comprises acetylating cellulose with acetic acid and acetic anhydride in the presence of a catalyst and propionic aldehyde.

12. Acetone-soluble cellulose acetate resulting from the acetylation of cellulose in the presence of 25-100 c.c. of an aldehyde per 100 grams of 

